1. Field of the Invention
The invention relates to a sheet member feeding and conveying apparatus which is mounted on an image reading apparatus, an image forming apparatus and the like and which conveys a sheet member such as a document and a recording sheet.
2. Description of the Related Art
An image reading apparatus which reads an image formed on a document by automatically conveying one document or a plurality of documents sequentially to an image reading section provided with an image sensor, and an image forming apparatus which forms an image on a recording sheet by automatically conveying one recording sheet or a plurality of recording sheets sequentially to an image forming section provided with an inkjet head are equipped with sheet member feeding and conveying apparatuses in order to read an image and form an image effectively. As digital technology progresses, the time between reading an image of a document and conversion to digital data and the time for forming an image from digital data on a recording sheet are shortened. Moreover, in an image reading apparatus and an image forming apparatus, in order to efficiently feed and convey a lot of sheet members including documents and recording sheets, the number of sheet members which can be held in a sheet member feeding and conveying apparatus at a time has remarkably increased, which is 100 or more in the case of a copy sheet of 62 g/m2 by basis weight, for example.
As such a prior art, a paper feeding apparatus provided with a deck on which a large number of sheet members can be placed and capable of manual paper feeding is disclosed in Japanese Unexamined Patent Publication JP-A 2-163227 (1990). Moreover, as another prior art, a paper feeding apparatus provided with a paper feeding table on which a large number of sheet members can be placed is disclosed in Japanese Unexamined Patent Publication JP-A 4-260547 (1992). Furthermore, as still another prior art, an automatic sheet material feeder provided with a document tray on which a plurality of sheet materials are placed is disclosed in Japanese Unexamined Patent Publication JP-A 10-194502 (1998).
In the aforementioned prior arts, a tray is placed in a waiting position where the spacing between a placed face of the tray and a pickup roller is the largest so that the user can make the tray hold the tray's maximum holding amount of sheet members when loading sheet members on the tray. Since the tray is placed in a waiting position even when the user loads and makes a few sheet members held, time of at least one second or more is required for displacing the tray from a waiting position to a position where the sheet members are placed in a take-out position where the pickup roller can take out the sheet members held on the tray. Therefore, the aforementioned time for displacing the tray is added to the duration from the time when the user makes sheet members held on the tray to the time when images formed on the sheet members are read or images are formed on sheet members, with the result that the time required for an image reading process and an image forming process becomes long. Particularly, in an image reading apparatus, it is exceedingly rare to read the maximum amount of sheet members which can be held on the tray, and the amount of sheet members to be read is normally one, a few or dozens at most.